Method of making sintered copper chromium metal composition



Patented Nov. 7, 1944 UNITED STATES PATENT OFFICE.

METHOD OF MAKING SINTERED COPPER GHROMIUM METAL COMPOSITION Franz 1t. Hensel and Earl I. Larsen, Indianapolis,

Ind., assignors to P. R. Mallory & 00., Inc., Indianapolis, Ind., a corporation of Delaware No Drawing. Application March 23, 1943,

. Serial No. 480,214

6 Claims. (or. 75-22) tion of phosphorus. A further improvement contemplated is the introduction of metal hydrides.

In attempts which have been made in the past to form copper chromium alloys by sintering the mixed metal powders, great difllculty has been experienced due to the formation of a soft shell on the metal body during sintering. It has been difficult to avoid this result without resort to elaborate precautions for protective atmospheres, rapid heating and the like. We have found that the soft shell can be avoided by incorporation of a small percentage of phosphorus in the powder mixture.

The sintered metal composition of the present invention is made from metal powders. The mixture used may contain copper, chromium and phosphorus in the following range of proportions:

Per cent Chromium 0.25 to 10 Phosphorus 0.05 to 3 Copper Balance In some cases silver may be substituted for part of the copper, the silver range extending from 0.1 to 8% silver, which is the range of solid solubility of silver in copper. If silver is present in excess of 8% the formation of silver-copper eutectic will interfere with heat treating.

It is also contemplated that the iron group metals nickel, cobalt and iron may be present singly or jointly. The total percentage of these ingredients may be within the range 0.05% to These aid in hardening and strengthening the ing. ingredient in the sintered body. Hydrides of other metal of the fourth and fifth group of the periodic table may be 'used in the same proportions instead of titanium hydride, such as:

Zirconium hydride Hafnium hydride Thorium hydride Columbium hydride Tantalum hydride 'The hydrides of the alkaline and alkaline earth metals are not as stable as those of the metals of the higher groups of the periodic table but may be used in like proportions instead of those previously mentioned if proper precautions are taken. They include the following hydrides:-

Calcium hydride Barium hydride Strontium hydride Sodium hydride Potassium hydride These are quite hygroscopic and decompose rapidly into hydrogen and the corresponding hydroxide when left standing in air at room temperature.

The hydrides of the fourth group metals titanium, zinconium, hafnium and thorium are the most useful. These are stable at room temperature, non-hygroscopic, easy to handle and dissociate gradually during sintering.

The preferred range of compositions is:

Per cent Chromium 0.25 to 3 Phosphorus 0.05 to 0.75 Copper Balance such as copper containing 15% phosphorus are mixed together to yield a mixture having the ingredients present in the proportions mentioned. Silver or an iron group metal are also added to the mixture if desired. The metal hydrides, if used, are also added to the mixture as powders. The mixture is preferably ball milled for several hours and is then' compacted in a die to a pressed body of the desired shape. A pressure in the order of .30 tons per square inch is suitable.

The pressed body is sintered in a hydrogen atmosphere at a temperature of 975 to 1000 C. after which it may be quenched or allowed to ingredients in the proportions repressed at a pressure of 30 to 60 tons per square inch, resulting in a higher density.

The body may then be heated to a temperature above 850 C. and preferably between 975 to 1000 C., for hour and water quenched.

It is then aged in air at 450 C. (between 300 and 600 C.) for 16 hours.

During sintering and heat treatment some or all of the phosphorus present in the original powder mixture is lost. However, it performs its function during the manufacture of the composition with the result that the undesirable soft shell is not formed at the surface of the sintered metal body.

Chromium oxidizes readily at high, temperatures, even in the presence of hydrogen if the hydrogen contains traces of oxygen or water vap01. If the chromium becomes oxidized during the high temperature sintering treatment, it will not diffuse or alloy with the copper. Phosphorus, however, is even more readily oxidized than chromium; therefore when phosphorus is added to the mixture, it oxidizes in preference to the chromium, thereby protecting the chromium and allowing the chromium to diffuse into the cop- 'per. Phosphorus forms an oxide, the exact composition of which is not known; however, it may be either P203 or P205. Both of these oxides would sublime at the temperature used in the sintering of copper chromium phosphorus pressed bodies; thus a portion or all of the phosphorus in the original powder mixture is losthowever, it performs its function during the "manufacture of the composition with the result that the undesirable 'soft .shell is not formed at the surfaceof the sintered metal body.

A metal composition, formed of a mixture of Per cent Chromium 3.00 Phosphorus 0.10 Copper Balance after aging, exhibited a hardness of 51 Rockwell -B and an electrical conductivity of 64.3%. It had an ultimate tensile strength of 48,000 pounds per square inch.

Per cent Chromium 3.0 Phosphorus 0.1 Titanium hydride 0.5 Copper Balance was fabricated into a sintered and age hardened metal body which had the following properties:

Hardness Rockwell B 68 Electrical conductivity 69.1% Ultimate tensile strength 52,000

When tested on a Krouse fatigue machine of the' rotating beam type this body had an endurance limit of 20,000 pounds per square inch as shown by the fact that it was stressed for more than 50 million cycles at this stress. The composition made without hydrides had a stress limit under similar tests of 15,000 cycles.

Compositions of the present invention have application as bearings, clutch facings, pressure exerting welding electrodes, electric contacts, gears, valve seats and for-other uses where high strength, good electrical conductivity and good fatigue strength are required.

While specific embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the claims.

What is claimed is:

1. The method of making a sintered copperchromium metal composition which comprises mixing powders to form a mixture containing copper, chromium, phosphorus and a metal hydride, then pressing and sintering said mixture.

2. The method of making a sintered copperchromium metal composition which comprises mixing powders containing copper, chromium, phosphorus and a metal hydride to produce 'a powder mixture containing 0.25 to 10% chromium, 0.05 to 3% phosphorus, 0.1 to 5% metal hydride and the balance substantially all copper, then pressing and sintering said mixture.

3. The method of making a. sintered copperchromium metal composition which comprises mixing powders containing copper, chromium, phosphorus and a metal hydride selected from the group consisting of the hydrides of titanium, zirconium, hafnium and thorium to produce-a powder mixture containing 0.25 to 10% chromium, 0.05 to 3% phosphorus, 0.1 to 5% of said metal hydride and the balance substantially all copper, then pressing and sintering said mixture.

4. The method of making a sintered copperchromium metal composition which comprises mixing powders containing copper, chromium, phosphorus and a metal hydride to produce a powder mixture containing 0.25 to 10% chromium, 0.05 to 3% phosphorus, 0.1 to 5% metal a temperature above 850 C. and aging at a temperature between 300 and 600 C.

5. The method of making a sintered copperchromium metal composition which comprises mixing powders containing copper, chromium, phosphorus and a metal hydride selected from the group consisting of the hydrides of titanium, zirconium, hafnium and thorium to produce a powder mixture containing 0.25 to 3% chromium, 0.05 to 0.75% phosphorus, 0.05 to 0.75% of said metal hydride and the balance substantially all copper, then pressing and sintering said mixture.

6. The method of making a sintered copperchromium metal composition which comprises mixing powders containing copper, chromium, phosphorus and a metal hydride to produce a powder mixture containing 0.25 to 3% chromium, 0.05 to 0.75% phosphorus, 0.05 to 0.75 metal hydride and the balance substantially all copper, then pressing and sintering said mixture, and subsequently quenching the sintered at a temperature between 300 and 600 C.

FRANZ R. HENSEL. EARL I. .LARSEN. 

